A SPAD is based on a p-n junction device biased beyond its breakdown region. The high reverse bias voltage generates a large enough electric field such that a single charge carrier introduced into the depletion layer of the device can cause a self-sustaining avalanche via impact ionization. The avalanche is quenched, either actively or passively to allow the device to be “reset” to detect further photons. The initiating charge carrier can be photo-electrically generated by a single incident photon striking the high field region. It is this feature which gives rise to the name “Single Photon Avalanche Diode.” This single photon detection mode of operation is often referred to as Geiger Mode.
U.S. Pat. No. 7,262,402 to Niclass et al. discloses an imaging device using an array of SPADs for capturing a depth and intensity map of a scene, when the scene is illuminated by an optical pulse. U.S. Patent Application No. 2007/0182949 to Niclass discloses an arrangement for measuring the distance to an object. The arrangement uses a modulated photonic wave to illuminate the object and an array of SPADs to detect the reflected wave. Various methods of analysis are disclosed to reduce the effects of interference in the reflected wave.
In microwave ovens, there is often a problem of liquids and the like overflowing from the holding vessel. This causes a mess and also means a loss of some of the contents, which may have other consequences.
Microwave ovens are typically fitted with timers and alarms which sound at the end of a time period. These serve as a warning and are often ignored. In addition, the time period is user set and is generally based on an estimate of cooking time. Cooking time varies widely, based on the food or drink concerned, whether it is frozen or not, size, oven power rating etc. As a result, a user predicted time is not much use in avoiding spills or to another extent, undercooking the contents. Manufactures provide recommended cooking times and recipe books also attempt to give guidelines as to cooking times. However, they are but that, i.e. guidelines, and do not solve the problem of spills.